Frozensand?

I don't know if any of you are aware of the FPS called UrT (UrbanTerror). It's a fast-paced multiplayer game developed by a company called FrozenSand.

My question is: How do they work any revenue at all? The game itself holds no ads or anything. It's free to download and play. Their website is adfree also. Donations?

What, making money? For coding? Why would you want to do that? Do you also wonder how people "worked revenue" from all that drug use and sex in the seventies?